Pneumatic tire with locked bead construction

Abstract

A tire ( 10 ) has three carcass reinforcing structures ( 15, 16, 17 ). The second carcass reinforcing structure ( 16 ) is folded radially outwardly around each bead core 16 ( 20 ), so that the edges ( 36 ) of the second carcass reinforcing structure ( 16 ) are each located between an apex ( 31 ) and the neighboring bead core. The third carcass reinforcing structure ( 17 ) has its turndown portions ( 27 ) folded radially inwardly around the turnup portion of the second carcass reinforcing structure ( 16 ) and the bead core, so that the edges ( 37 ) of the plies of the third carcass reinforcing structure are located at the radially inner side of the bead cores ( 20 ). The first carcass reinforcing structure ( 15 ) has its turnup portions ( 25 ) folded radially outwardly around each bead core, the turnupportion of the second carcass reinforcing A structure ( 16 ) and the turndown portion of the third carcass reinforcing structure ( 17 ) so that the edges ( 35 ) of the plies of the first carcass reinforcing structure are located near the radially outer portion of the apex ( 31 ).

What is claimed is:  
     
       1. A pneumatic tire having: 
       (a) a pair of axially spaced apart bead portions with annular bead cores, each bead core having a radial cross-sectional shape which is substantially round or polygonal;  
       (b) a pair of rubber apex strips of a generally triangular cross-section neighboring the bead cores the apex strips having a radial height A and extending radially outwardly from the bead cores into the sidewalls of the tire; and  
       (c) at least three sets, a first radially inner, a second intermediate and a third radially outer set of carcass reinforcing structures, having each a main portion extending between the beads and their edges anchored in the beads, the tire characterized by;  
       the first carcass reinforcing structure being folded radially outwardly around each said bead core. so that the two edges of the second carcass reinforcing structure are located between the apexes and their neighboring bead cores;  
       the second carcass reinforcing structure having turndown portions folded radially inwardly around the second carcass reinforcing structure and the bead cores, so that the edges of the plies of the third carcass reinforcing structure are located near the axially inner side of the bead cores;  
       the third carcass reinforcing structure having turnup portions folded radially outwardly around each bead core, the second carcass reinforcing structure and the third carcass reinforcing structure so that the edges of the plies of the first carcass reinforcing structure are located between the radially outer portion of the bead core and the maximum section height of the tire.  
     
     
       2. The pneumatic tire of  claim 1  wherein the first, second and third carcass reinforcing structure comprise each one ply. 
     
     
       3. The pneumatic tire of  claim 2  wherein the edges of the plies of the first carcass reinforcing structure are located between one third and full radial height A of the apex strips. 
     
     
       4. The pneumatic tire of  claim 1  wherein the apex strip extends radially from the bead core to a maximum height between 25% and 55% of the maximum section height of the tire. 
     
     
       5. The pneumatic tire of  claim 1  wherein the apex strip extends radially from the bead core to about 3000 of the maximum section height of the tire. 
     
     
       6. The pneumatic tire of  claim 1  wherein the carcass reinforcing structures are reinforced with nylon cords. 
     
     
       7. The pneumatic tire of  claim 6 , wherein each bead core has a cross-sectional shape which is substantially rectangular. 
     
     
       8. The pneumatic tire of  claim 7 , wherein the tumup portions of the second carcass reinforcing structure extend on at least 50% of the maximum axial bead core width C. 
     
     
       9. The pneumatic tire of  claim 1 , wherein each bead core is at least partially reinforced with steel wire. 
     
     
       10. The pneumatic tire of  claim 1  wherein each bead core has a cross-sectional shape which is substantially polygonal. 
     
     
       11. The pneumatic tire of  claim 1 , wherein the edges of the plies of the third carcass reinforcing structure are located near the radially inner edges of the bead cores. 
     
     
       12. The pneumatic tire of  claim 1 , wherein the bead portion comprises a toe guard which is at least partly wound around the bead core so as to cover the edge of the first carcass reinforcing structure furthest away from the bead core. 
     
     
       13. A pneumatic tire having: 
       (a) a pair of axially spaced apart bead portions with annular bead cores, each bead core having a radial crop sectional shape which is substantially round or polygonal;  
       (b) a pair of rubber apex strips of a generally triangular cross section neighboring the bead cores the apex strips having a radial height A and extending radially outwardly from the bead cores into the sidewalls of the tire;  
       (c) a bead wrap ply structure;  
       (d) at least two sets, a first radially inner and a second radially outer set of carcass reinforcing structures, having each a main portion extending between the beads and their edges anchored in the beads, the tire characterized by:  
       the first carcass reinforcing structure being folded radially outwardly around each said bead core, so that the two edges of the first carcass reinforcing structure are located between the apexes and their neighboring bead cores;  
       the second carcass reinforcing structure having turndown portions folded radially inwardly around the first carcass reinforcing structure and the bead cores, so that the edges of the plies of the second carcass reinforcing structure are located near the axially inner side of the bead cores;  
       the bead wrap ply structure having turnup portions folded radially outwardly around each bead core, the first carcass reinforcing structure and the second carcass reinforcing structure so that the edges of the plies of the bead wrap ply structure are located between the radially outer portion of the bead core and the maximum section height of the tire, the bead wrap ply structure extending axially inward and radially outward from the radially inner portion of the bead core to a radial distance at least one half the radial height of the bead core.